Repeated effects of asenapine on adrenergic and cholinergic muscarinic receptors.

Adrenergic (alpha1 and alpha2) and cholinergic muscarinic (M1-M5) receptor binding in rat forebrain was quantified after 4 wk of twice-daily subcutaneous administration of asenapine or vehicle. Asenapine (0.03, 0.1, and 0.3 mg/kg) produced increases in [3H]prazosin binding to alpha1-adrenergic receptors in the medial prefrontal cortex (mPFC: 30%, 39%, 57%) and dorsolateral frontal cortex (DFC: 27%, 37%, 53%) and increased [3H]RX821002 binding to alpha2-adrenergic receptors in mPFC (36%, 43%, 50%) and DFC (41%, 44%, 52%). Despite showing no appreciable affinity for muscarinic receptors, asenapine produced regionally selective increases in binding of [3H]QNB to M1-M5 receptors in mPFC (26%, 31%, 43%), DFC (27%, 34%, 41%), and hippocampal CA1 (40%, 44%, 42%) and CA3 (25%, 52%, 48%) regions. These regionally selective effects of asenapine on adrenergic and cholinergic muscarinic receptor subtypes may contribute to its beneficial clinical effects in the treatment of schizophrenia and bipolar disorder.

Chimeric mice with humanized liver.

Recently, chimeric mice with humanized liver were established by transplanting human hepatocytes into an urokinase-type plasminogen activator(+/+)/severe combined immunodeficient transgenic mouse line. The replacement with human hepatocytes is more than 80-90% and is higher than any other chimeric mouse reported previously. In drug development, the liver is one of the most important organs because it is mainly involved in the pharmacokinetics of drugs and is frequently damaged by many drugs due to the accumulation of drugs and/or metabolites. The pharmacokinetics could affect the efficacy and toxicity of a drug, and thus prediction of the human pharmacokinetics is important for developing new drugs without adverse reactions and toxicity. Extrapolation from experimental animals or in vitro studies to the human in vivo pharmacokinetics is still difficult. To date, human hepatocytes and liver microsomes are recognized as better tools and are frequently used to estimate the human pharmacokinetics. We thought that chimeric mice with humanized liver could become a new tool for estimating the human toxicity and pharmacokinetics. At first, metabolism, which plays an essential role in pharmacokinetics, was investigated in the chimeric mice. In the liver of the chimeric mice, human drug metabolizing enzymes were found to be expressed and to reflect the capacities and genetic polymorphism of the donor. In an in vivo study on metabolism, human specific metabolites could be detected in the serum of the chimeric mice indicating that the chimeric mice could be used as an in vivo model to address human metabolism. These results suggested that the chimeric mice could overcome the species differences in drug metabolism and be used to evaluate drug toxicity due to genetic polymorphism. The reasons for drug interaction are often enzyme induction and inhibition. By the treatment with a typical inducer of cytochrome P450 (P450), which is the central drug-metabolizing enzyme, P450s expressed in the liver of the chimeric mice were found to possess induction potencies. After the treatment with a specific inhibitor of human P450, the area under the curve of the P450 metabolite was significantly decreased in the chimeric mice but not in the control mice. Therefore, it was indicated that the chimeric mice could be useful for assessing drug interactions in vivo. Moreover, drug excretion was determined to be humanized because cefmetazole was mainly excreted in urine both in the chimeric mice and humans but in the feces in control uPA(-/-)/SCID mice. Drug transporters expressed in the liver of the chimeric mice were also humanized. In this review, studies of the chimeric mice with humanized liver, particularly on metabolism and excretion, are summarized and the possibility of using the chimeric mice is proposed for the advanced prediction of human pharmacokinetics and toxicity.

In vivo drug metabolism model for human cytochrome P450 enzyme using chimeric mice with humanized liver.

We previously clarified that major human drug metabolizing enzymes were expressed in a chimeric urokinase-type plasminogen activator (uPA)+/+/severe combined immunodeficient (SCID) mouse line established recently, in which the liver could be replaced by more than 80% with human hepatocytes. In the present study, we investigated the in vivo drug metabolism of a CYP2D6 substrate, debrisoquin (DB), in chimeric mice with high (High) or low (Low) human albumin (hAlb) concentrations and in control uPA-/-/SCID mice. The hAlb in the mouse blood is one of the indices of humanized liver because the chimeric mice produce hAlb. After oral administration of DB at 2.0 mg/kg, the AUC0-8 value of a major CYP2D6 metabolite of DB, 4'-hydroxydebrisoquin (4-OH DB), in High was 3.6-fold higher than those of Low and uPA-/-/SCID mice. By pre-treatment with a typical CYP2D6 inhibitor, quinidine, the AUC0-8 value of 4-OH DB in High was decreased although such values in Low and uPA-/-/SCID mice did not change. The in vitro kinetic analyses and the Ki values of quinidine on the DB 4'-hydroxylase activity in liver microsomes also supported the humanization of the chimeric mice. In conclusion, the chimeric mice exhibited a humanized profile of drug metabolism and the inhibition of P450.

A convenient method for local drug administration at predefined sites in the entire gastrointestinal tract: experiences from 13 phase I studies.

For local administration of drugs or enzyme inhibitors in the human gut, a small-bore, smooth tube was introduced through the nose, retrieved from the pharynx, equipped with a firm radio-opaque capsule, and swallowed. Peristalsis moves the capsule to the desired location in the gut where it is anchored before administration via the tube. Drug uptake is followed by plasma sampling. One capsule type is used for solutions, another for solid formulations. With solutions, repeated administrations could be done with the capsule being anchored for 24h or longer or, alternatively, at several locations along the gut. This communication presents the method and an overview of 13 uptake and enzyme/transporter localization studies. Altogether, 268 intubations were undertaken in a total of 128 subjects. Plasma concentrations found with terbutaline and metoprolol are presented showing that terbutaline has its best uptake in the upper small intestine, whereas metoprolol shows the same bioavailability along the whole gut. Subjects could undertake most of their normal activities while carrying the equipment. No serious adverse events (AEs) occurred. Possibly intubation-related AEs were abdominal pain (n=8) and constipation (n=5). In conclusion, the method has been found to be safe, convenient and multifunctional for studies of drug uptake at predetermined gut locations in healthy subjects.

CYP2D6 polymorphism is not crucial for the disposition of selegiline.

OBJECTIVE: To determine the possible impact of CYP2D6 polymorphism on the pharmacokinetics and pharmacodynamics of selegiline. METHODS: Five poor metabolizers and 8 extensive metabolizers of debrisoquin (INN, debrisoquine) were given 10 mg selegiline hydrochloride. The concentrations of selegiline and its main metabolites in serum were determined for 4 days. The pharmacodynamics were quantitated by measuring platelet monoamine oxidase type B activity for 3 weeks. In addition, the effect of selegiline and its main metabolites on the CYP2D6-catalyzed dextromethorphan O-demethylase activity and the effect of quinidine on the metabolism of selegiline were studied in human liver microsomes. RESULTS: Peak serum concentrations of selegiline were reached rapidly and ranged from 1 to 32 nmol/L. The metabolite concentrations were considerably higher and remained so for a longer period. There were no significant differences in the pharmacokinetic parameters of selegiline, desmethylselegiline, and l-amphetamine between poor metabolizers and extensive metabolizers. However, the area under the serum concentration-time curve (AUC) values of l-methamphetamine were, on average, 46% higher (P = .01) in poor metabolizers than in extensive metabolizers. No significant correlations were found between debrisoquin metabolic ratio and AUC values of selegiline or its metabolites, except for l-methamphetamine (rs = 0.90; P < .001). The maximum monoamine oxidase type B inhibition was 97% in both groups. The inhibitory potency of selegiline, desmethylselegiline, and l-methamphetamine toward dextromethorphan O-demethylase was very low (50% inhibitory concentration values from 160 to 580 mumol/L). Quinidine (< or = 100 mumol/L) did not inhibit the formation of desmethylselegiline or l-methamphetamine from selegiline. CONCLUSIONS: CYP2D6 is not important in the primary elimination of selegiline, and the biological effect of selegiline seems to be similar in poor metabolizers and extensive metabolizers of debrisoquin. The inhibitory effect of selegiline and its main metabolites on CYP2D6 activity seems to be negligible.

Disposition of fluvoxamine in humans is determined by the polymorphic CYP2D6 and also by the CYP1A2 activity.

BACKGROUND: Fluvoxamine is a selective serotonin reuptake inhibitor used widely in the treatment of depression and other psychiatric diseases, but little is known about the specific isozymes involved in its metabolism. This study investigated the relationship between fluvoxamine disposition and the polymorphic CYP2D6 and the polycyclic aromatic hydrocarbon (as contained in cigarette smoke) inducible CYP1A2. METHODS: Fluvoxamine (50 mg orally) was given to 10 extensive metabolizers and four poor metabolizers of debrisoquin, and concentrations were assessed in plasma by high performance liquid chromatography. Five of the extensive metabolizers and one of the poor metabolizers were smokers of more than 10 cigarettes per day. The CYP1A2 activity was determined by means of a urinary caffeine test. RESULTS: Compared with nonsmoking extensive metabolizers, nonsmoking poor metabolizers had a statistically significant (p = 0.02, Mann-Whitney U test) about twofold higher maximum plasma concentration, longer half-life, and fivefold lower oral clearance of fluvoxamine. The oral clearance of fluvoxamine correlated to the CYP1A2 index in the 14 subjects (rs = 0.58; p < 0.05; Spearman rank correlation). CONCLUSION: The disposition of fluvoxamine in humans is associated with the polymorphic CYP2D6 activity, but CYP1A2 also seems to be involved.

In vivo assessment of botanical supplementation on human cytochrome P450 phenotypes: Citrus aurantium, Echinacea purpurea, milk thistle, and saw palmetto.

OBJECTIVES: Phytochemical-mediated modulation of cytochrome P450 (CYP) activity may underlie many herb-drug interactions. Single-time point phenotypic metabolic ratios were used to determine whether long-term supplementation of Citrus aurantium , Echinacea purpurea , milk thistle (Silybum marianum), or saw palmetto (Serenoa repens) extracts affected CYP1A2, CYP2D6, CYP2E1, or CYP3A4 activity. METHODS: Twelve healthy volunteers (6 women, 6 men) were randomly assigned to receive C aurantium , E purpurea , milk thistle, or saw palmetto for 28 days. For each subject, a 30-day washout period was interposed between each supplementation phase. Probe drug cocktails of midazolam and caffeine, followed 24 hours later by chlorzoxazone and debrisoquin (INN, debrisoquine), were administered before (baseline) and at the end of supplementation. Presupplementation and postsupplementation phenotypic trait measurements were determined for CYP3A4, CYP1A2, CYP2E1, and CYP2D6 by use of 1-hydroxymidazolam/midazolam serum ratios (1-hour sample), paraxanthine/caffeine serum ratios (6-hour sample), 6-hydroxychlorzoxazone/chlorzoxazone serum ratios (2-hour sample), and debrisoquin urinary recovery ratios (8-hour collection), respectively. The content of purported "active" phytochemicals was determined for each supplement. RESULTS: Comparisons of presupplementation and postsupplementation phenotypic ratios suggested that these particular supplements had no significant effect on CYP1A2, CYP2D6, CYP2E1, or CYP3A4 activity. Phytochemical profiles indicated that C aurantium was devoid of the CYP3A4 inhibitor 6',7'-dihydroxybergamottin. Quantities of fatty acids, flavonolignans, and cichoric acid were consistent with label claims for saw palmetto, milk thistle, and E purpurea , respectively. CONCLUSIONS: Botanical supplements containing C aurantium , milk thistle, or saw palmetto extracts appear to pose a minimal risk for CYP-mediated herb-drug interactions in humans. Although the effects of E purpurea on CYP activity were minor, further study into the interaction potential of this botanical is merited.

Cetirizine/pseudoephedrine.

Cetirizine is the carboxylated metabolite of hydroxyzine, and has high specific affinity for histamine H(1) receptors. Pseudoephedrine is a sympathomimetic drug that acts directly on alpha-adrenergic receptors. black triangle Cetirizine/pseudoephedrine 5/120 mg twice daily was significantly more effective than intranasal budesonide 100 microg or placebo at improving nasal obstruction, nasal patency and reducing the volume of nasal secretion, and was significantly more effective than intranasal xylometazoline 0.1% with respect to nasal secretion, during house dust mite faeces challenge in three randomised, cross- over studies among volunteers with seasonal or perennial rhinitis. The onset of action of cetirizine/pseudoephedrine was reported to be approximately 30 minutes. black triangle The bioavailability of cetirizine and pseudoephedrine is similar after administration of cetirizine/pseudoephedrine 5/120 mg bilayer tablets or coadministration of cetirizine 5 mg tablets plus pseudoephedrine sustained-release (SR) 120 mg caplets. black triangle Cetirizine 5mg plus pseudoephedrine SR 120 mg twice daily for 2 to 3 weeks was significantly more effective than each drug given alone at reducing mean total symptom scores for seasonal or perennial allergic rhinitis in two randomised, double-blind, multicentre trials. In both studies, the mean proportion of days during which the five measured symptoms (nasal obstruction, sneezing, rhinorrhoea, nasal pruritus and ocular pruritus) were absent or mild was significantly greater in recipients of the cetirizine plus pseudoephedrine SR. black triangle In one study, cetirizine 5 mg plus pseudoephedrine SR 120 mg was significantly more effective at reducing nasal obstruction than either drug alone. black triangle Cetirizine 5mg plus pseudoephedrine SR 120 mg twice daily for 2 to 3 weeks was well tolerated in patients with seasonal or perennial allergic rhinitis. The most common adverse events were dry mouth, insomnia, headache, somnolence, asthenia and nervousness.

Single-dose pharmacokinetics of modafinil and methylphenidate given alone or in combination in healthy male volunteers.

Modafinil is a novel wake-promoting agent being developed for treatment of excessive daytime sleepiness associated with narcolepsy. An open, 3 x 3 Latin square, randomized, cross-over study was performed in healthy males to compare the pharmacokinetics of single-dose oral modafinil (200 mg) and methylphenidate (40 mg) administered alone or in combination. Blood samples were obtained for analysis of d- and l-threo-methylphenidate and modafinil and its acid and sulfone metabolites. Pharmacokinetic parameters were determined by noncompartmental methods, but could not be evaluated for modafinil sulfone due to plasma levels that were close to the assay quantitation limit. Although sporadic differences in plasma concentrations were observed between treatments, coadministration of modafinil and methylphenidate did not significantly alter the plasma concentrations of modafinil, modafinil acid, modafinil sulfone, or methylphenidate enantiomers compared with administration of these agents alone. Half-life (t1/2), maximum concentration (Cmax), area under the concentration-time curve (AUC0-infinity), total clearance (Cl/F), and apparent volume of distribution (Vd/F) for modafinil and t1/2, Cmax, and AUC0-infinity for modafinil acid were not affected by concomitant administration of methylphenidate. Small but statistically significant increases in time to Cmax (tmax) were observed for modafinil and modafinil acid after methylphenidate coadministration compared with modafinil alone. Modafinil coadministration did not significantly alter the pharmacokinetics of d- or l-threo-methylphenidate, except for a small decrease in Vd/F of l-threo-methylphenidate. Concomitant methylphenidate may cause a delay in the oral absorption of modafinil, but this delay might not be relevant clinically. Coadministration did not alter the extent of oral absorption and disposition of either agent. Therefore, a pharmacokinetic interaction between modafinil and methylphenidate would be unlikely.

Complexities in the neurotoxic actions of 6-hydroxydopamine in relation to the cytoprotective properties of taurine.

The neurotoxin 6-hydroxydopamine was shown to cause an imbalance between the direct and indirect pathways of the striato-nigral system as evidenced by a decreased release of gamma-aminobutyric acid and taurine in the substantia nigra but not in the globus pallidus following neostriatal stimulation with kainate (100 microM). The neurotoxicity of 6-hydroxydopamine is generally believed to result from reactive-oxygen radical formation, although it is also known to inhibit mitochondrial NADH dehydrogenase. The release of Fe(II) from the unactivated form [3Fe(III)-4S] of cytoplasmic aconitase (EC(50) < 8 microM) was shown to be followed by the slower oxidation of thiol groups in the protein. Complete loss of -SH groups, and enzyme activity, was seen after incubation of glyceraldenyde-3-phosphate dehydrogenase with 200 microM 6-hydroxydopamine for 75 min at 37 degrees C (IC(50) = 70.8 +/- 0.3 microM). Thus the cellular effects of 6-hydroxydopamine are complex, involving impairment of mitochondrial function, iron- release, sulphydryl-group oxidation, and enzyme inhibition in addition to direct generation of reactive oxygen radicals. Taurine, which is known to be neuroprotective in some other systems, only affords protection against some of these effects, thereby explaining its reported ineffectiveness against 6-hydroxydopamine toxicity.

Influx and efflux of amphetamine and N-acetylamphetamine in keratinocytes, pigmented melanocytes, and nonpigmented melanocytes.

To establish an in vitro model of drug incorporation into hair and to elucidate the potential roles of hair cell selectivity and hair color in the incorporation of certain drugs into hair, the basic drug amphetamine and its nonbasic analog N-acetylamphetamine (N-AcAp) were analyzed for influx and efflux into and out of keratinocytes, pigmented melanocytes (PM), and nonpigmented melanocytes (NPM) as a model for incorporation and efflux of these drugs from hair cells. NPM were of the same melan-a cell line as PM, but cultured in the presence of the tyrosinase inhibitor phenylthiocarbamide. Results show that PM take up large amounts of the basic drug amphetamine (levels of uptake dependent on melanin content), whereas keratinocytes and NPM take up only small amounts of amphetamine. None of the cells take up N-AcAp above background levels. Interestingly, whereas keratinocytes and NPM quickly efflux most of the influxed drug, PM are slow to efflux and only efflux approximately 65% of influxed drug, if efflux media is not refreshed. (If efflux media is periodically refreshed, PM will eventually redistribute essentially all influxed drug back into the media.) These results demonstrate that pigmented cells take up greater amounts of the basic drug amphetamine, and efflux it more slowly than nonpigmented cells. Also, these results are consistent with previous data for in vivo incorporation of amphetamine in animal hair. In combination with previous data, an overall comparison of the amphetamine and N-AcAp incorporation data support a non-diffusion mediated model for drug incorporation into hair cells.

Do synthetic adrenergic agents interfere with the measurement of endogenous plasma catecholamine concentrations?

PURPOSE: It is common to administer synthetic sympathomimetic and sympatholytic agents in the intensive care unit and operating room. The present study examines whether such agents, as well as the products of catecholamine metabolism, interfere with the quantitation of endogenous catecholamines by high-performance liquid chromatography. METHODS: Samples of drugs and metabolites were assayed before and after alumina extraction and their relative retention times were compared with dopamine, norepinephrine, and epinephrine relative retention times. Blood samples from patients receiving these drugs were also assayed for their interferences with catecholamine determination. RESULTS: Phenylephrine interfered with the quantitation of epinephrine. Isoproterenol's peak was so delayed it appeared in the following chromatogram. Dobutamine had two small peaks in vitro, whereas in the patient samples only one peak was identified; the other was probably masked by the dopamine peak. Labetalol had one peak when the pure drug was assayed but multiple peaks in patient samples, that were probably caused by metabolites of labetalol. CONCLUSION: Synthetic adrenergic agents and catecholamine metabolites can potentially interfere with the quantitation of the endogenous catecholamines. Thus, it is important to examine whether such interference occurs when conducting high-performance liquid chromatography assays.

[Transplantation of fetal dopaminergic cells simultaneously to the corpus striatum and pars reticularis of the substantia nigra in hemi-parkinsonian rats]. / Trasplante de células dopaminérgicas fetales simultáneamente en striatum y substantia nigra pars reticulata en ratas hemiparkinsonianas.

INTRODUCTION: Transplantation of foetal dopaminergic cells has been extensively used as restorative treatment for Parkinson's disease. OBJECTIVE: This study was carried out to determine the survival, modifications in rotatory activity induced by D-amphetamine and total content of dopamine in the striatal and nigra regions of hemiparkinsonian rats which had had foetal mesencephalic cells simultaneously transplanted to the striatum and pars reticularis of the substancia nigra. MATERIAL AND METHODS: The study was done using adult male Wistar rats weighing 200-250 gms. The following experimental groups were formed, depending on the site of transplant: St: transplant to striatum (n = 2); SNr: transplant to SNr (n = 20), ST + Snr; transplant to striatum and SNr simultaneously n = 20; and control (lesion with no transplant) n = 20. We studied the rotatory activity induced by D-amphetamine 1, 2, 3 and 6 months after transplantation. After this time the rats were deeply anaesthetized and randomly allocated for morphological study or biochemical determination of the total dopamine content in the St and SNr using the HPLC technique. RESULTS: Study of conduct showed no significant differences in rotatory activity induced by D-amphetamine between the groups with intrastriatal transplants, but there was a difference between these and the SNr and control groups. Biochemical analysis showed that striatal DA content was significantly greater in the ST for the groups with intrastriatal transplants. The content of substancia nigra DA was significantly greater in the SNr of the ST + SNr group, followed by the ST group. Morphometric study showed differences, which were not significant, between ST transplanted animals and significant differences between the SNr transplanted group with a significant increase in survival of the SNr of the ST + SNr group. CONCLUSIONS: These results suggest a positive effect due to intrastriatal transplants compared to survival following intranigral transplants.

α1-Adrenergic receptor subtypes in the central nervous system: insights from genetically engineered mouse models.

α1-Adrenergic receptors (α1-ARs) are important players in peripheral and central nervous system (CNS) regulation and function and in mediating various behavioral responses. The α1-AR family consists of three subtypes, α1A, α1B and α1D, which differ in their subcellular distribution, efficacy in evoking intracellular signals and transcriptional profiles. All three α1-AR subtypes are present at relatively high densities throughout the CNS, but the contributions of the individual subtypes to various central functions are currently unclear. Because of the lack of specific ligands, functionally characterizing the α1-ARs and discriminating between the three subtypes are difficult. To date, studies using genetically engineered mice have provided some information on subtype-related functions of the CNS α1-ARs. In this mini-review, we discuss several CNS processes where the α1-ARs role has been delineated with pharmacological tools and by studies using mutated mice strains that infer specific α1-AR subtype functions through evaluation of behavioral phenotypes.

Mechanisms of withdrawal-associated increases in heroin self-administration: pharmacologic modulation of heroin vs food choice in heroin-dependent rhesus monkeys.

Opioid withdrawal can produce a constellation of physiological and behavioral signs, including an increase in opioid self-administration. Different mechanisms mediate different withdrawal signs, and the present study used pharmacologic tools to assess mechanisms underlying withdrawal-associated increases in opioid reinforcement. Five rhesus monkeys were rendered heroin dependent via daily 21-h heroin self-administration sessions. One hour after each heroin self-administration session, monkeys chose between heroin (0-0.1 mg/kg per injection) and food (1 g pellets) during 2-h choice sessions. Under these conditions, heroin maintained a dose-dependent increase in heroin choice, such that monkeys responded primarily for food when low heroin doses were available (0-0.01 mg/kg per injection) and primarily for heroin when higher heroin doses were available (0.032-0.1 mg/kg per injection). Periods of spontaneous withdrawal were intermittently introduced by omitting one 21-h heroin self-administration session, and test drugs were administered during these withdrawal periods. Untreated withdrawal robustly increased heroin choice during choice sessions. Withdrawal-associated increases in heroin choice were completely suppressed by the mu opioid agonist morphine (0.032-0.32 mg/kg/h, i.v.), but not by the alpha-2 noradrenergic agonist clonidine (0.01-0.1 mg/kg/h, i.v.), the dopamine/norepinephrine releaser amphetamine (0.032-0.1 mg/kg/h, i.v.), or the kappa-opioid antagonist 5'-guanidinonaltrindole (1.0 mg/kg, i.m.). The corticotropin-releasing factor 1 antagonist antalarmin (1.0-10 mg/kg per day, i.m.) produced a morphine-like suppression of withdrawal-associated increases in heroin choice in one of three monkeys. These results suggest that mechanisms of withdrawal-associated increases in the relative reinforcing efficacy of opioid agonists may be different from mechanisms of many other somatic, mood-related, and motivational signs of opioid withdrawal.

Impaired maze performance in aged rats is accompanied by increased density of NMDA, 5-HT1A, and alpha-adrenoceptor binding in hippocampus.

Using quantitative receptor autoradiography, we assessed binding site densities and distribution patterns of glutamate, GABA(A), acetylcholine (ACh), and monoamine receptors in the hippocampus of 32-month-old Fischer 344/Brown Norway rats. Prior to autoradiography, the rats were divided into two groups according to their retention performance in a water maze reference memory task, which was assessed 1 week after 8 days of daily maze training. The animals of the inferior group showed less long-term retention of the hidden-platform task but did not differ from superior rats in their navigation performance during place training and cued trials. The decreased retention performance in the group of inferior learners was primarily accompanied by increased alpha(1)-adrenoceptors in all hippocampal subregions under inspection (CA1-CA4 and dentate gyrus), while elevated alpha(2)-adrenoceptor binding was observed in the CA1 region and DG. Furthermore, inferior learners had higher NMDA binding in the CA2 and CA4 and increased 5-HT(1A) binding sites in the CA2, CA3, and CA4 region. No significant differences between inferior and superior learners were evident with regard to AMPA, kainate, GABA(A), muscarinergic M(1), dopamine D(1), and 5-HT(2) binding densities in any hippocampal region analyzed. These results show that increased NMDA, 5-HT(1A), and alpha-adrenoceptor binding in the hippocampus is associated with a decline in spatial memory. The increased receptor binding observed in the group of old rats with inferior maze performance might be the result of neural adaptation triggered by age-related changes in synaptic connectivity and/or synaptic activity.

Relationship between the swelling process and the release of a water-soluble drug from a compressed swellable-soluble matrix of poly(vinyl alcohol).

An attempt was made in this study to relate the release of a highly water-soluble model drug from tablet matrices of poly(vinyl alcohol) (PVAL) with the factors that may affect the release behavior. Swelling was evaluated using a simple projection method. The swollen layer was photographed to monitor its thickness. The polymer and drug dissolution were determined simultaneously by spectrophotometric methods. The resulting change of tablet area showed that the process of swelling occurred in three different stages that were intimately related to polymer dissolution: (a) a rapid initial swelling, resulting in an increased area; (b) a period with an approximately constant area; and (c) a decrease of the tablet area. In spite of the significant dissolution of PVAL during the release process, the thickness of the gel layer gradually increased. Thus, the delivery was governed by the drug concentration gradient along the diffusional path length. The drug release appeared to be controlled by a diffusion process according to Higuchi-type kinetics. The data analysis of drug and polymer profiles confirmed the diffusional mechanism.

Gender differences in drug effects: implications for anesthesiologists.

BACKGROUND: The gender aspect in pharmacokinetics and pharmacodynamics of anesthetics has attracted little attention. Knowledge of previous work is required to decide if gender-based differences in clinical practice is justified, and to determine the need for research. METHODS: Basis for this paper was obtained by Medline searches using the key words 'human' and 'gender' or 'sex,' combined with individual drug names. The reference lists of these papers were further checked for other relevant studies. RESULTS: Females have 20-30% greater sensitivity to the muscle relaxant effects of vecuronium, pancuronium and rocuronium. When rapid onset of or short duration of action is very important, gender-modified dosing may be considered. Males are more sensitive than females to propofol. It may therefore be necessary to decrease the propofol dose by 30-40% in males compared with females in order to achieve similar recovery times. Females are more sensitive than males to opioid receptor agonists, as shown for morphine as well as for a number of kappa (OP2) receptor agonists. On this basis, males will be expected to require 30-40% higher doses of opioid analgesics than females to achieve similar pain relief. On the other hand, females may experience respiratory depression and other adverse effects more easily if they are given the same doses as males. CONCLUSION: These examples illustrate that gender should be taken into account as a factor that may be predictive for the dosage of several anesthetic drugs. Moreover, there is an obvious need for more research in this area in order to further optimize drug treatment in anesthesia.

The CYP2D6 humanized mouse: effect of the human CYP2D6 transgene and HNF4alpha on the disposition of debrisoquine in the mouse.

CYP2D6 is a highly polymorphic human gene responsible for a large variability in the disposition of more than 100 drugs to which humans may be exposed. Animal models are inadequate for preclinical pharmacological evaluation of CYP2D6 substrates because of marked species differences in CYP2D isoforms. To overcome this issue, a transgenic mouse line expressing the human CYP2D6 gene was generated. The complete wild-type CYP2D6 gene, including its regulatory sequence, was microinjected into a fertilized FVB/N mouse egg, and the resultant offspring were genotyped by both polymerase chain reaction and Southern blotting. CYP2D6-specific protein expression was detected in the liver, intestine, and kidney from only the CYP2D6 humanized mice. Pharmacokinetic analysis revealed that debrisoquine (DEB) clearance was markedly higher (94.1 +/- 22.3 l/h/kg), and its half-life significantly reduced (6.9 +/- 1.6 h), in CYP2D6 humanized mice compared with wild-type animals (15.2 +/- 0.9 l/h/kg and 16.5 +/- 4.5 h, respectively). Mutations in hepatic nuclear factor 4alpha (HNF4alpha), a hepatic transcription factor known to regulate in vitro expression of the CYP2D6 gene, could affect the disposition of CYP2D6 drug substrates. To determine whether the HNF4alpha gene modulates in vivo pharmacokinetics of CYP2D6 substrates, a mouse line carrying both the CYP2D6 gene and the HNF4alpha conditional mutation was generated and phenotyped using DEB. After deletion of HNF4alpha, DEB 4-hydroxylase activity in CYP2D6 humanized mice decreased more than 50%. The data presented in this study show that only CYP2D6 humanized mice but not wild-type mice display significant DEB 4-hydroxylase activity and that HNF4alpha regulates CYP2D6 activity in vivo. The CYP2D6 humanized mice represent an attractive model for future preclinical studies on the pharmacology, toxicology, and physiology of CYP2D6-mediated metabolism.